In a Long Term Evolution (LTE) system, a user equipment (UE) may transmit and receive data over multiple carriers (Component Carrier, CC) by using a carrier aggregation (CA) technology, thereby achieving a better balance between carriers and improving network performance. The carriers may also be called component carriers or carrier units.
In an existing base station eNB, a Packet Data Convergence Protocol (PDCP) entity and a Radio Link Control (RLC) entity are managed in a centralized manner, and scheduling of a Medium Access Control (MAC) entity and a layer 1 (L1) entity are managed in a decentralized manner. In a multicarrier scenario (for example, N carriers are available), the PDCP entity and the RLC entity may be deployed on a same board (typically a baseband board) with one carrier, and other carriers are separately deployed on different boards. The maximum number of carriers that is supported by a current LTE standard is used as an example, when a peak rate of a single user equipment is 3 Gbps, a Radio Link Control entity of the user equipment outputs a data volume of 3 megabits during a transmission time interval (TTI); if only one carrier and the RLC entity are on a same board, the volume of data outputted to other boards is 2.4 megabits. If transmission delay is 100 ms as required, a bandwidth required for data transmission between boards is 24 Gbps. If 3 sectors are considered to be supported, a higher bandwidth is required for data transmission between boards.
Currently it is rather difficult for a baseband unit (BBU) in a base station to meet such a high bandwidth requirement.